The invention disclosed herein relates to apparatus for storing and transferring cassettes of strip or ribbon material containing pigment, wax, resin, ink, etc. for use with printers and plotters. More particularly, the invention relates to storing and automatically transferring a selected cassette between a storage location thereof and a use location thereof on a movable print carriage to which a print head is mounted.
Modern color and monochrome computer or digital printing apparatuses are of the matrix type which print an overall image on media in small dots or other small geometric configurations. Matrix printers typically are of the line mode or serial mode type. A line mode printer uses a stationary print head as wide the medium to be printed upon and prints an entire line at a time. A serial mode printer uses a movable so called flying or raster scan print head having a width substantially less than that of the medium to be printed upon which is moved along a line to be printed effectively continuously as the printer prints up to the full width of the medium. As disclosed in application Ser. No. 07/920,186, a matrix printer may also print in a novel strip mode. The print head of a strip mode printer is narrower than the full width of the medium to be printed on, but wider than a typical raster scan print head. The image and/or text to be printed by the strip mode printer is divided into strips each having a width up to the width of the print head. The strip mode print head prints in strips, strip by strip, i.e., part of a line in a strip is printed with the print head held stationary in that strip, then the print head is moved or indexed along the line to another strip of the line which is printed while the print head is held stationary in that strip. Thus, the print head of a strip mode printer is movable and must be moved from strip to strip in order to print on the full width of the medium. Strip mode printing is described in detail in application Ser. No. 07/920,86.
Except for direct thermal printers, typical contact-type printers (line mode and movable print head printers) employ a print head which contacts strip or ribbon material containing a substance such as pigment, wax, resin, ink, etc. which is interposed between the print head and the medium, and transfers the substance from the strip or ribbon material to the medium being imprinted. For simplicity, such substance will hereinafter be referred to as "ink", and such strip or ribbon material, which may be a film, ribbon, etc., will hereinafter be referred to as a "ribbon". Such contact-type printers include impact wire- or pin-dot matrix printers and thermal transfer printers. In order for such contact-type printers to print an image in more than one color, they employ either a ribbon having portions of a plurality of different color inks or a plurality of ribbons of different color inks.
A single multi-colored ribbon has the advantage that ribbon mounting and indexing is relatively simple because only a single ribbon has to be mounted, controlled and guided, and only a single print head is required, as opposed to mounting a plurality of ribbons of different color and either selecting the ribbon with the desired color or providing a different print head for each ribbon. Printers using a single multi-colored ribbon for color printing typically index the entire ribbon past the print head including portions of the ribbon having colors that are not then being printed. Either those unused portions are not used at all, which is wasteful, may require frequent ribbon reloading and may be quite expensive due to high ribbon cost, or the ribbon has to be indexed back to those unused portions for later use, which requires a means to identify unused portions of the ribbon and the color of such unused portions, and a bi-directional indexing means.
Use of a plurality of ribbons avoids the problems discussed above with multi-colored ribbons. However, where a different print head is used for each different colored ribbon, cost may be a problem particularly for thermal printers. Also, where space is a factor, mounting a number of print heads and ribbons in a small space may be difficult. Where a single print head is used, the ribbons must be mounted so that a selected one may be used at a time. In single print head, line mode printers for printing on media of substantial width, the ribbon mounting arrangement would have to provide for satisfactory control and guidance of the selected ribbon for substantially the full width of the media, which would substantially complicate any such mounting arrangement. In single print head, movable print head printers, the ribbon spans a much shorter distance than in line mode printers so that ribbon control and guidance is not as serious a problem as in line mode printers. However, the ribbon mounting arrangement for movable print head printers must provide for ribbon selection relative to a moving print head, rather than the stationary print head of a line mode printer.
Thus, color contact-type printers which employ either a single multi-colored ribbon or a plurality of different colored ribbons have drawbacks.
The following U.S. patents disclose printers which employ a multi-colored ribbon: U.S. Pat. Nos. 4,378,566; 4,542,997; 4,558,329; 4,620,199; 4,707,703; and 4,710,781.
The following U.S. patents disclose printers which employ a plurality of ribbons and a corresponding plurality of print heads, one for each ribbon: U.S. Pat. Nos. 3,926,109 (line mode); 4,067,017 (line mode); 4,403,874 (serial mode); 4,447,818 (line mode); 4,540,992 (line mode); and 4,694,305 (serial mode).
IBM Technical Disclosure Bulletins Vol. 21, No. 11, pp. 4448-4451, April 1979, J. H. Meier et al., and Vol. 22, No. 10, pp. 4481-4482, March 1980, J. H. Meier disclose printers which employ a number of individual stationary print heads arranged to print in line mode fashion and a plurality of ribbons.
U.S. Pat. No. 4,815,869 discloses a printer which employs a single print head and a plurality of ribbons which are used one at a time and are manually loaded into and unloaded from the printer.
The following U.S. patents disclose printers which employ a single print head and a plurality of ribbons: U.S. Pat. Nos. 3,726,212 (line mode); 4,469,459 (serial mode) 4,564,303 (serial mode); 4,647,232 (serial mode); 4,692,774 (serial mode); and 4,809,018 (line mode).
As indicated above, U.S. Pat. Nos. 4,469,459, 4,564,303, 4,647,232 and 4,692,774 disclose serial mode printers which utilize a single print head and a plurality of ribbons. In the '303 patent, two ribbons are mounted within the same cartridge which is moved to position a selected ribbon aligned with the print head. In the ''450, '232 and '459 patents, the ribbon cassettes are all mounted on a movable carriage which also carries the print head, which have the disadvantage that the carriage must be relatively large to accommodate a large number of ribbon cassettes, particularly where the ribbons are of a significant width.
U.S. Pat. Nos. 4,135,245; 4,288,798; 4,573,129; 4,660,054; and 4,683,476 disclose pen plotter apparatus which includes a movable plotter head carrying a pen-type instrument and a pen-exchanging apparatus which automatically exchanges a similar pen-type instrument stored off the plotter head with the pen-type instrument currently being carried by the plotter head. As compared to exchange systems for ribbons for color printers, such exchange apparatus is relatively simple given the small size and simple geometric configuration of the pen-type instruments, and given that the pen-type instruments have no moving parts and no ribbon which must be controlled and guided.
The invention seeks to provide an improved apparatus for mounting a plurality of ribbons and automatically positioning a selected ribbon aligned with a movable print head, particularly for use with thermal transfer printers, especially the strip mode printer disclosed in Ser. No. 07/920,186.